Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
A typical wireless carrier network includes a number of base stations that radiate to define wireless coverage areas, such as cells and cell sectors, in which wireless coverage devices (WCDs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, mobile hotspots, and other wirelessly-equipped communication devices, can operate. Each base station may be coupled with equipment that provides connectivity with one or more transport networks such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a WCD operating in a coverage area of the wireless carrier network may engage in air interface communication, via the wireless carrier network, with other WCDs operating in the wireless carrier network as well as with various remote network entities sitting outside of the wireless carrier network.
The wireless carrier network may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to WCDs defining a downlink (or forward link) and communications from the WCDs to the base stations defining an uplink (or reverse link). Examples of existing air interface protocols include, without limitation, Code Division Multiple Access (CDMA) (e.g., 1xRTT and 1xEV-DO), Long Term Evolution (LTE), WiMAX, iDEN, TDMA, AMPS, Global System for Mobile Communications (GSM), GPRS, UMTS, EDGE, MMDS, WI-FI, and BLUETOOTH. The architecture of the wireless carrier network may vary depending on the protocol employed.
During interaction between WCDs and a wireless carrier network, various types of messages may be exchanged These message types may take various forms, which may depend on factors such as the air interface protocol employed and the operating state of the WCD. For instance, after a given WCD operating in an idle state enters a coverage area of the wireless carrier network, the given WCD may send control messages such as a registration message and/or a message identifying the location of the WCD to the wireless carrier network. Thereafter, the given WCD may send control messages to facilitate the establishment of an active connection with the wireless carrier network, such as an access probe, a page response message, a channel assignment request, etc. If the WCD does transition into an active state and establish an active connection with the wireless carrier network, the WCD may then exchange other types of control messages (as well as bearer data) with the wireless carrier network, such as control messages to facilitate a handover. Finally, when the active connection between the given WCD and the wireless carrier network is to be terminated (e.g., because the exchange of bearer data is complete or due to a radio link failure), the given WCD may exchange control messages with the wireless carrier network related to that termination. It should be understood that these and other messages are described merely for purposes of illustration, and that a WCD may be configured to send various other types of messages to a wireless carrier network as well.